Electric servo



C. L. PAULUS ELECTRIC ssnvo Nov. so, 1948.

' heo t s-sheot 1 Filed Feb. 20, 1945 INVEN TOR. 41/191165 L. PHUL 05 BY ha 74M; W Wfm 1 7 7' 7' Off/f Y5 C- L. PAULUS ELECTRIC SERVO Nov. 30, 1948.

4 Sheets-Sheet 2 Filed Feb 20, 1946 IN V EN TOR. 6/76/4165 L. PHI/L 05 BY M QTTOENEYS CENTER/1Y6 sw/ 76/1 Nov. 30, 1948. c. L. PAULUS 2,454,832

ELECTRIC SERVO Filed Feb. 20. 1946 4 Shqets-She'et 3 QTTOE/VEYJ Nov. 30, 1948.

C. L. PAUL-US ELECTRIC SERVO 4 Sheets-Sheet 4 Filed Feb. 20, 1946 E J a 6 4 N x W Va E Patented Nov. 30, 1948 UNIT ED S TAT E S PATENT IO FF 1 C E ELECTRIC SERVO Charles L. PaulusyDayton, Ohio Application February 20, 1946, Serial No. 649,107

(Granted under the act of. March 3, 1883,--as

amended April 30, 1928; 3'70 O.-G. 757) 3 Claims.

This invention relates to electric servos, the

embodiment shown being particularly adapted to remotely controlled vehicles such as small radio controlled airplane targets.

An object of the invention is to provide a structure wherein all parts may 'be assembled on a frame structure and given final inspection and test before the outer casing which shields against dirt and moisture'is applied thereto.

Another'object is to provide a novel sealing means between the dust cover and the main frame and around the output shaft where it emerges from the mainframe.

Another object is to provide an electrical outlet as part of the main frame.

Another object is to provide a centering switch which will automatically stop the power take-off arm in the mid position o'f its travel.

Another object is to provide a limit switch which will automatically stop the power take-off arm at preselected points in its travel away from its mid position.

Another object is to so position the limit and centering switches and the necessary gearing on the main frame that space is left for the wiring which must necessarily terminate at the electrical outlet.

Another object is to position the motor on the subf-rame by using the 'antifriction bearing of the motor as a dowel between the motor and the main frame.

' Another object is to provide a mounting for the motor which requires no ears or projections on the motor itself.

Other objects and advantages will appear as the invention is described ingreater detail and reference is made to the drawings, wherein;

' Fig. 1 is a left-hand end view of an embodiment of my invention showing the power takeoff arm, the electrical outlet and the mounting bracket,

Fig. 2 is in part a side view and in part a longitudinal sectional view extending through the cam operated switches, the gearing and the electrical outlet, that part of the view which is taken through the switches and the gearing beingtaken on the line 22 of Fig. 1 and that part which is taken through the electrical outlet .being taken on the line 2-2a of Fig.1,

Fig. 3 is a transverse section through the cam v2 operated limit "switch taken at 33 of Fig. 2 showing both sides of the switch open,

Fig. 4 is a transverse section through the cam operated centering switch taken at 44 of Fig. 2 showing both sides of the switch closed,

Fig. 5 is a transverse section through a part of the speed'reducing gearing' taken on the line 5-5 of-Fig; 2,

r Fig; 6 is a'transverse section taken at 5-6 of Fig. 2 through the first of. the speed-reducing gears and the motor pinion whichu'drives it, the motor being shown in dotted lines,

Fig. 7 is apartial longitudinal section taken at L l of Fig.6 to show the motor mounting,

Fig. 8 is a detail :view of the controlled rod mounting,

Fig. 9 is a wiringxdiagram of the electric circults,

' which may preferably be produced by die casting or: similarmeans is provided with axially extendin'g bosses 1-2 to the free ends of which a subframe I4 is secured by screws Hi. The subframe I4 is a circular disc which may conveniently be punched from relatively thick sheet metal or it may be otherwise fabricated.

The output shaft' I 80f the device has bearing at the forward-end in a'boss 20 carried on the inside face of the main frame Ill and at the rearward end 22, has bearing in an opening in the subframe 14. .A conventional seal 24 is press fitted into a boss I 9 'on' the frame 10 and surrounds the shaft I8 where it emerges from the main housing i ll in c-rd'er'to make a waterproof seal around the oscillating shaft.

The outer end of the output shaft l'B is enlarged andexternally serrated as at 26 to correspond to internal serrations in the inside of the hub of the'output lever 28. The end of the output lever 28 is split as'at 30 so that a screw 32 may clamp thelever 30 on the shaft in a selected position.

in -order to :protect the mechanism against shock, the lower or power take-off end of the lever -28 (see Fig; 8) is provided with a liner 2| of rubber'or other resilient material, and a second liner 23 of metal within the first liner. A stud 25 is fitted to the-metal liner. 23 and is held in place by thehead ZTand a nut 29. A ball end 3-! is held in the bottom of asocket 33 by a plug 3 5 which is pressed against the ball by a spring '1. The spring 31 is held in the socket by a pin 2. The socket 33 is slotted at M for the stud A rod 43 conveys the power impulses from t e socket 33 to the various controls which the device is designed to operate.

Mounted along-side the hub 20 on the shaft I8 is a collar 34 (see Fig. 2) which is fastened to the shaft it by a pin 36. Cut integral on the collar 32 are a centering cam 38 and a limit cam 48. Centering cam 38 (see Fig. 3) operates a centering switch 42 which is insulatedly secured to a lug a l which is part of the main frame It. Limit cam it (see Fig. 4) operates a limit switch 46 which is insulatedly secured to the lug 44 alongside the centering switch 42.

The centering switch 42 is made up of an upper flexible blade 48, a lower flexible blade 59 and a middle flexible blade 52, the three blades being insulated from each other, from the lug 44, and from the screws 56 which fasten the blades to the lug as shown.

A dielectric rider 56 (see Fig. 3) is carried on the free end of the middle blade 52 and, in the center position shown, rests on a lobe 31 of the cam 33.

When the cam 38 is in the mid position shown, the rider 56, resting on the lobe 31, holds the middle blade 52 out of contact with both the upper blade 48 and the lower blade 50. The middle blade 52, however, is tensioned to spring downward, whereby, when the cam 38 rotates clockwise, the rider 56 will drop to the lower position 39 of the cam whereby the middle blade 52 will engage the lower blade 5t, while, if the cam rotates anticlockwise, the rider 56 will be raised, whereby the middle blade 52 will be forced upward away from the lower blade 50 and will engage the upper blade 48.

To facilitate description and identification in the claims, the blades 48, 50, and 52 will herein after be referred to respectively as the centering switch first, second, and third contact members. The limit switch 46 comprises an upper flexible blade 58, a lower flexible blade 60 and a middle flexible blade 62, the three blades being insulated from the lug 44 and from the screws 5 which fasten the blades to the lug as shown.

A dielectric rider 64 (see Fig. 4) is carried on the free end of the middle blade and rests on the cam 4H. When the cam 40 is in the mid position shown, the rider 64 holds the middle blade 62 in electrical engagement with both the upper blade 58 and the lower blade 60. The middle blade 52 however, is tensioned to spring downi ward whereby when the cam 40 rotates clockwise, as much as 30 from the central position shown, the rider M will drop to the lower lobe 66 of the cam whereby the middle blade 62 will drop away from the upper blade 58, thus severing electrical contact between them, but will continue to engage the lower blade 60. On the other hand, if the cam 45 rotates anticlockwise as much as 30 from the central position shown, the rider 64 will be raised to the upper lobe 68 of the cam, thus separating electrical connections between the middle blade 62 and the lower blade 60 but maintaining electrical connection between the middle blade I32 and the upper blade 58.

For purposes of identification in the claims, the limit switch blades 58, 60, and 62 will hereinafter be referred to respectively as the limit switch first, second, and third contact members.

Secured to the main shaft I8 for rotation therewith is a main drive gear I0 (see Fig. 2) which 4 may be silver soldered or similarly secured to the shaft. Alongside the main drive gear I0 is a pinion l2 and a gear l4 which are freely rotatable on the main shaft. Pinion I2 and gear I4 may be made integral or be made separately and fastened together to rotate as one.

A countershaft l6 has one end supported in a boss 78 on the main frame I0 and the other end in an opening in the subframe I4. A pinion 8t and gear 82 are in mesh respectively with the gear "Ill and pinion l2. Pinion 80 and gear 82 are freely rotatable on the countershaft It and may be made integral or fastened together in any suitable manner to rotate as one.

A pinion 84 and gear 06 are freely rotatable on the countershaft I5. They may be made integral or may be fastened together to rotate in unison. Pinion 84 is in mesh with the gear 14 while the teeth of the gear 86 are engaged by the teeth of a pinion 88 (see Fig. 6) which is carried on the shaft 90 of an electric motor 92 (see Fig. 7).

The electric motor 92 is secured to the subframe I4 by screws 94. A relay 96 also carried by the subframe I4 is fastened thereto by screws til. The windings and connections of the motor 92 and the relay 96 will be best understood from the wiring diagram, Fig, 9.

The motor 92 is of the permanent magnet field type and is therefore reversible only by changing the direction of the current through the armature, the relay 05 being provided for this purpose. As may be seen in the wiring diagrams, Figs. 9 through 13, the relay, when no current is passing through its coil, is spring biased to cause the common contacts I29 and I3I to engage the contacts Hi l and I26 as seen in Figs. 9, l0, and 13 for producing clockwise movement of the motor and output lever 28, but, when current is directed through its coil, will cause the common contacts i29 and I3! to make contact with the lower contacts I28 and I30 as seen in Figs. 11 and 12 for anticlockwise rotation of the motor and lever 28.

For convenience in description and for identification in the claims and without intent to impose any structual limitation, the contacts I24 and I 26 will hereinafter be referred to respectively as the relay first and second contact members, and the contacts I 28 and 530 will be referred to respectively as the relay third and fourth contact members. The common contacts I29 and I3! will be referred to respectively as the relay fifth and sixth contact members.

The motor terminals I33 and I35 will be referred to respectively as the motor first and sec ond terminals.

A unique manner of positioning the motor on the subframe I4 to insure correct meshing of its pinion 88 with the gear is shown in Fig. 7. Here the ball bearings I00 is allowed to protrude slightly from its seat in the motor and a corresponding counterbore in the subframe I4 is provided to receive the protruding part of the hearing.

The electrical terminal boss I02 (see Fig. 2) is of a standard type and is designed to be waterproof. The contact pins, designated in the wiring diagram as A, B, C, and D are imbedded in dielectric I06 and bring in the current from the outside of the housing to the relay 96 and motor 92 and to the centering and limit switches 42 and 4G. The wiring of the motor relay and switches is shown in the diagrams, Figs. 9 through 13.

The bracket I08 (see Fig. 1) by which the unit is mounted on the aircraft or other mechanism which it is to control consists of a metal strip annu ar groove is. provided to receive the seal ring H4; The seal. ring is made of rubber or other gasket material and extendsoutwardly beyond the groove. After the entire device is completely assembled and tested and mounted on the aircraft where it is. to. be used, a dust cover H6 may be slid over the subframe I4 and frame I8 with the open end of the cover against the projectingportion of the seal ring H4 and, the cover drawn up. to. the ring by screws I [6.

The advantage oi this housing construction is obvious. tested and even put into actual use without the dust cover in place. In this way, the device may be seen inaction before the cover is put on.

In thewiring diagram A is the terminal which is permanently connected to the one side of a source of electrical energy. B, C, and D are selectively connectible to the other side for moving the control rod 43 (see Fig. 8) to the left center or right, respectively. Switch means H8, I20, and 122 are provided whereby whenever the said other side is not selectively connected to B or D, it is automatically connected to C which is of the same polarity as B and D. Switches H8 and I22 are schematically shown as being spring biased to the open position, and switch I28 as being spring biased to the closed position. Switches H8 and I 22 as shown are manually closable, but it will be understood that they may, within appropriate radio signal receiving means be closable by the sender of radio signals from a distance.

The operation of the servo unit is substantially as follows:

Assuming the device to be in the inactive state as seen in Fig. 9, wherein both sides of the centering switch 42 are open, both sides of the limit switch 46 are closed, and the contacts I29 and I3I of the relay 96 are spring biased to the upper position and therefore closed onto the contacts I24 and I26. The terminal A is shown as permanently connected to the positive side of the current source.

If it is now desired to rotate the output arm clockwise, the terminal B may be selectively connected to the negative side of the power source as by a switch H8 as shown in Fig. 10 whereby current will flow to the relay contacts I26 and HI, through the motor from the contact I35 to the contact I33, to rotate it clockwise, then through the relay contacts I29 and I24, limit switch blade 58 and 62 to the positive power terminal A.

As soon as the motor 92 starts, the centering cam 38 will cause the blade 52 of the centering switch 42 (see Fig. 3) to make electrical contact with the blade 50 as seen in Fig. 10, and this contact will re main in effect as long as the operating arm 28 is turned clockwise off the central or home position shown in Fig. 1. However, when the output shaft I8 becomes turned as much as 30 from the home position, the limit switch cam 40 will cause the blade 62 to be withdrawn out of contact with the blade 58 as seen in Fig. 11 which will break the circuit through the motor 92 causing it to cease rotation.

The mounting.

The entire unit may be assembled and In; order now, toreturn the output lever; 28, to.

the central or home position, the switch I18 of.

the negative terminal B is merely. released whereupon the switch I28 of the negative term nal C auto atic y e ag s, and rrent;

passes through, the blades 52 and 53 of, the cen.-. ering switch 42 and through the coil of the, re;

lay 96 which shifts the relay to cause the contacts I29 and I3I to engage, the contacts I28; and I38 so that current may pass through contactmcmbers I28; and 129 and through the motor from terminal I 33 to terminal I35 through terminals. I3I and [30; and through limit switch blades fill; and 52 to the positive terminal A which will ro tate the motor anticlockwise and return the out.- put lever 28 to the home position.

As soon as the output shaft I8 starts to, return from the 30 position, toward the 11011151107. sition, the limit cam 4Ilwi1l cause the limit switch blade 62 to re-engage the blade 58 and when the will again be closed as in. Fig. 9.

When it is desired to rotate the output lever 28, anticlockwise, the terminal D may be selectively connected to the negative side of the power source as by the switch I22 (see Fig. 12) whereby current will first flow to the coil of the relay 88-. to close the relay contacts i129. and HI onto the contacts I28; and I30, whereby current will flow through the motor from the motor terminal I33 to motor terminal I35 for anticlockwise rotation of the motor the output lever.

As soon as anticlockwise rotation begins, the blade 53 of; the centering switch 42 (see Fig. 3) engages the blade 48 as shown in Fig. 12 and this contact will maintain as long, as the operating arm 28 is turned anticlockwise off the central or home position seen in Fig. 1. However, when the output shaft l8 becomes turned anticlockwise as much as 30 from the home position, the limit switch blade 52 will be withdrawn out of contact with the blade til as seen in Fig. 13, which will break the circuit through the motor 92 causing it to. cease rotation, and will break the circuit through the coil of the relay 96 thereby allowing the contacts I24 and I25 to be re-engaged by the contacts ms. and I3I.

In order now to return the output lever 28 to the central or home position, the switch I22 of the negative terminal D is released, whereupon, the switch I2il of the negative terminal C automatically engages and the current passes through the blades 52 and 48 of the centering switch 42 to the contacts I26 and I3I through the motor from terminal I35 to terminal I33 for clockwise operation and through the contacts [29 and I24. and terminals 58 and 62 of the limit switch 46 back to positive terminal A whereby the output arm is returned to the home position.

From the foregoing description, it will be seen that closing the switch H8 to negatively energize the terminal B will rock the lever 28 clockwise and opening the switch at any position of the lever 28 will return the lever to the home position, provided, however, that it cannot be rocked clockwise more than 30 from the home position because the limit switch it breaks the circuit at that point by separating the contact blades 62 and 58. Moreover, at the beginning of its rocking movement, the centering switch 42 connects its blades 52 and 50 so that when the terminal B is de-energized and the terminal C thereby 3 automatically energized, the relay will reverse the current in the motor to return the lever to the home position.

It is equally obvious that energizing the ter minal D by means of the switch I22 will rock the lever 28 anticlockwise as much as 30, but no more and will return it from any position to the home position upon de-energization of terminal D and the consequent automatic energization of terminal C.

It will, of course, be understood that while the wiring diagram shows the terminal A as positive and terminals B, C, and D as negative, the arrangement is equally operative if A is negatively energized and B, C, and D are positively energized.

Having described an embodiment of my invention whereby the objects hereinbefore set forth are attained, I claim:

1. In an electric servo unit having a frame, an

=output shaft having bearings in said frame and adapted to rock in said bearings, an electric motor,

lsaid motor having first and second terminals carried by said frame, and a speed reducing gear train connecting said motor to said output shaft, the improved control mechanism which comprises :a first power terminal of one polarity, a second, a third and a fourth power terminal of the other polarity, a relay coil, relay first second contact members, relay third and fourth contact members, relay fifth and sixth contact members, yieldable means biasing said relay fifth and sixth contact members into engagement with said relay first and second contact members respectively, a relay core operative upon energization of said coil to move said relay fifth and sixth contact members into engagement with said relay third and fourth contact members, respectively, centering switch first and second contact members, a centering switch third contact member normally out of electrical contact with the centering switch first and second contact members, a centering switch cam operative when rotated one direction to engage said centering switch third contact memher with said centering switch second contact member and operative when rotated in the other direction to engage said centering switch third contact member with said centering switch first contact member, limit switch first and second contact members, a limit switch third contact member norm-ally in electrical contact with the limit switch first and second contact members, a limit switch cam operative when rotated in one direction to disengage the limit switch third contact member from the limit switch first contact memher, and operative when rotated in the other direction to disengage the limit switch third contact member from the limit switch second contact member, and electrical conductors connecting said first power terminal to the limit switch third contact member; connecting said second power terminal to the centering switch first contact member and the relay second contact member; connecting said third power terminal to the centering switch third contact member; connecting the said fourth power terminal to the said centering switch second contact member, to one end of said relay coil and to said relay third contact member; connecting the other end of said relay coil to the said relay fourth contact member and to the limit switch second contact member; connecting the said relay first contact member to the said limit switch first contact member; and connecting the said relay fifth and sixth contact members to the motor first and second terminals, respectively.

2. In an electric servo power unit, first, second, third and fourth power terminals, fixed means for applying an E. M. F. of one polarity to the first power terminal, selective means for applying an E. M. F. of the other polarity to the second or fourth power terminals, means automatically responsive to release of both said selective means for applying an E. M. F. of said other polarity to said third power terminal, an electric motor, motor first and second terminals, a relay, a relay coil, first, second, third, fourth, fifth, and sixth contacts carried by said relay, a relay core normally operative to yieldably engage the relay fifth and sixth contacts with the relay first and second contacts but operative upon energization to engage the relay fifth and sixth contacts with the relay third and fourth contacts, a centering switch including centering switch first, second, and third contacts, the third contact being normally out of engagement with the first and second contact, a centering cam operative when rotated in one direction to engage said centering switch third contact with. said centering switch second contact and operative when rotated in the other direction to engage said centering switch third contact with said centering switch first contact, a limit switch including limit switch first, second, and third contacts, the limit switch third contact being normally in engagement with the limit switch first and second contact, a limit cam operative when rotated in one direction to disengage the limit switch third contact from the limit switch first contact, and operative when rotated in the other direction to disengage the limit switch third contact from the limit switch second contact, and electrical conductors connecting said first power terminal to the limit switch third contact; connecting said second power terminal to the centering switch first contact and the relay second contact; connecting said third power terminal to the centering switch third cont-act; connecting the said fourth power terminal to the said centering switch second contact, to one end of said relay coil and to said. relay third contact; connecting the other end of said relay coil to the said relay fourth contact and to the limit switch second contact; connecting the said relay first contact to the said limit switch first contact; and connecting the said relay fifth and sixth contacts to the motor first and second terminals respectively.

3. The device of claim 2 wherein the centering and limit switches are on a low speed shaft and a speed reducing gear train connects the motor to the said low speed shaft.

CHARLES L. PAULUS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,644,265 Rieber Mar. 27, 1928 2,251,054- I-Iorowitz et a1 July 29, 1941 2,354,364 Chapman July 25, 1944 

